A seamless graphene/nanotube hybrid created at Rice University may be the best electrode interface material possible for many energy storage and electronics applications.

Led by Rice chemist James Tour, researchers have successfully grown forests of carbon nanotubes that rise quickly from sheets of graphene to astounding lengths of up to 120 microns, according to a paper published today by Nature Communications. A house on an average plot with the same aspect ratio would rise into space.

Seven-atom rings (in red) at the transition from graphene to nanotube make this new hybrid material a seamless conductor. The hybrid may be the best electrode interface material possible for many energy storage and electronics applications. Image courtesy of the Tour Group

The Rice hybrid combines two-dimensional graphene, which is a sheet of carbon one atom thick, and nanotubes into a seamless three-dimensional structure. The bonds between them are covalent, which means adjacent carbon atoms share electrons in a highly stable configuration. The nanotubes aren’t merely sitting on the graphene sheet; they become a part of it.

“Many people have tried to attach nanotubes to a metal electrode and it’s never gone very well because they get a little electronic barrier right at the interface,” Tour said. “By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material.

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In the new work, the team grew a specialized odako that retained the iron catalyst and aluminum oxide buffer but put them on top of a layer of graphene grown separately on a copper substrate. The copper stayed to serve as an excellent current collector for the three-dimensional hybrids that were grown within minutes to controllable lengths of up to 120 microns.

Electron microscope images showed the one-, two- and three-walled nanotubes firmly embedded in the graphene, and electrical testing showed no resistance to the flow of current at the junction.

“The performance we see in this study is as good as the best carbon-based supercapacitors that have ever been made,” Tour said. “We’re not really a supercapacitor lab, and still we were able to match the performance because of the quality of the electrode. It’s really remarkable, and it all harkens back to that unique interface.”

For anyone who’s not familiar with the Morph, it’s an idea that Nokia and the University of Cambridge’s Nanoscience Centre have been working on for the last few years. Originally announced as a type of flexible phone that you could wrap around your wrist, the Morph is now called a concept. Here’s an animation illustrating some of the concepts which include flexibility and self-cleaning,

There have been very few announcements of any kind about the Morph or the technology that will support this concept. A few months ago, they did make an announcement about researching graphene as a means of actualizing the concept (noted in my May 6, 2011 posting [scroll down about 1/2 way]).

Interestingly the latest research published on graphene and the flexible, transparent screens that are necessary to making something like the Morph a reality has come from a lab at Rice University. From the August 1, 2011 news item on Nanowerk,

The lab of Rice chemist James Tour lab has created thin films that could revolutionize touch-screen displays, solar panels and LED lighting. The research was reported in the online edition of ACS Nano (“Rational Design of Hybrid Graphene Films for High-Performance Transparent Electrodes”).

Flexible, see-through video screens may be the “killer app” that finally puts graphene — the highly touted single-atom-thick form of carbon — into the commercial spotlight once and for all, Tour said. Combined with other flexible, transparent electronic components being developed at Rice and elsewhere, the breakthrough could lead to computers that wrap around the wrist and solar cells that wrap around just about anything. [emphasis mine]

The lab’s hybrid graphene film is a strong candidate to replace indium tin oxide (ITO), a commercial product widely used as a transparent, conductive coating. It’s the essential element in virtually all flat-panel displays, including touch screens on smart phones and iPads, and is part of organic light-emitting diodes (OLEDs) and solar cells.

Here’s James Tour and Yu Zhu, the paper’s lead author, explaining how the flexible screen was developed,

There are other flexible screens and competitors to the Morph notably the PaperPhone mentioned in my May 6,2011 posting (scroll down about 2/3 of the way) and in my May 12, 2011 posting featuring an interview with Roel Vertegaal of Queen’s University, Ontario, Canada, about the PaperPhone. (We did not discuss the role that graphene might or might not play in the development of the Paperphone’s screens.)

I wonder what impact this work at Rice will have not only for the Morph and the PaperPhone but on the European Union’s pathfinder research competition (the prize is $1B Euros), mentioned in my June 13, 2011 posting about graphene (scroll down about 1/3 of the way). Graphene is one of the research areas being considered for the prize.

The cookie gambit started on a dare when Tour mentioned at a meeting that his lab had produced graphene from table sugar.

“I said we could grow it from any carbon source — for example, a Girl Scout cookie, because Girl Scout Cookies were being served at the time,” Tour recalled. “So one of the people in the room said, ‘Yes, please do it. … Let’s see that happen.'”

Members of Girl Scouts of America Troop 25080 came to Rice’s Smalley Institute for Nanoscale Science and Technology to see the process. Rice graduate students Gedeng Ruan, lead author of the paper, and Zhengzong Sun calculated that at the then-commercial rate for pristine graphene — $250 for a two-inch square — a box of traditional Girl Scout shortbread cookies could turn a $15 billion profit.